diff --git a/src/embed_tests/TestFinalizer.cs b/src/embed_tests/TestFinalizer.cs
@@ -101,7 +101,17 @@ public void CollectOnShutdown()

            PythonEngine.Shutdown();
            garbage = Finalizer.Instance.GetCollectedObjects();
-            Assert.IsEmpty(garbage);
        }

        [MethodImpl(MethodImplOptions.NoInlining | MethodImplOptions.NoOptimization)] // ensure lack of references to obj
@@ -173,7 +183,7 @@ public void SimpleTestMemory()
            bool oldState = Finalizer.Instance.Enable;
            try
            {
-                using (PyObject gcModule = PythonEngine.ImportModule("gc"))
                using (PyObject pyCollect = gcModule.GetAttr("collect"))
                {
                    long span1 = CompareWithFinalizerOn(pyCollect, false);

diff --git a/src/embed_tests/TestNativeTypeOffset.cs b/src/embed_tests/TestNativeTypeOffset.cs
@@ -9,7 +9,7 @@

using Python.Runtime;

-namespace Python.EmbeddingPythonTest
{
    public class TestNativeTypeOffset
    {

diff --git a/src/embed_tests/TestPythonException.cs b/src/embed_tests/TestPythonException.cs
@@ -46,7 +46,7 @@ public void TestPythonErrorTypeName()
        {
            try
            {
-                var module = PythonEngine.ImportModule("really____unknown___module");
                Assert.Fail("Unknown module should not be loaded");
            }
            catch (PythonException ex)
@@ -95,7 +95,7 @@ public void TestPythonExceptionFormatNoTraceback()
        {
            try
            {
-                var module = PythonEngine.ImportModule("really____unknown___module");
                Assert.Fail("Unknown module should not be loaded");
            }
            catch (PythonException ex)

diff --git a/src/embed_tests/TestRuntime.cs b/src/embed_tests/TestRuntime.cs
@@ -96,7 +96,7 @@ public static void PyCheck_Iter_PyObject_IsIterable_ThreadingLock_Test()
            // TypeFlags.HaveIter set in Python 2. This tests a different code path in PyObject_IsIterable and PyIter_Check.
            var threading = Runtime.Runtime.PyImport_ImportModule("threading");
            Exceptions.ErrorCheck(threading);
-            var threadingDict = Runtime.Runtime.PyModule_GetDict(new BorrowedReference(threading));
            Exceptions.ErrorCheck(threadingDict);
            var lockType = Runtime.Runtime.PyDict_GetItemString(threadingDict, "Lock");
            if (lockType.IsNull)
@@ -110,6 +110,8 @@ public static void PyCheck_Iter_PyObject_IsIterable_ThreadingLock_Test()
            Assert.IsFalse(Runtime.Runtime.PyObject_IsIterable(lockInstance));
            Assert.IsFalse(Runtime.Runtime.PyIter_Check(lockInstance));

            Runtime.Runtime.Py_Finalize();
        }
    }

diff --git a/src/embed_tests/pyimport.cs b/src/embed_tests/pyimport.cs
@@ -52,7 +52,7 @@ public void Dispose()
        [Test]
        public void TestDottedName()
        {
-            PyObject module = PythonEngine.ImportModule("PyImportTest.test.one");
            Assert.IsNotNull(module);
        }

@@ -62,7 +62,7 @@ public void TestDottedName()
        [Test]
        public void TestSysArgsImportException()
        {
-            PyObject module = PythonEngine.ImportModule("PyImportTest.sysargv");
            Assert.IsNotNull(module);
        }


diff --git a/src/embed_tests/pyinitialize.cs b/src/embed_tests/pyinitialize.cs
@@ -175,7 +175,8 @@ public static void TestRunExitFuncs()
            {
                called = true;
            };
-            atexit.InvokeMethod("register", callback.ToPython());
            Runtime.Runtime.Shutdown();
            Assert.True(called);
        }

diff --git a/src/runtime/BorrowedReference.cs b/src/runtime/BorrowedReference.cs
@@ -28,6 +28,14 @@ public BorrowedReference(IntPtr pointer)
            => a.pointer == b.pointer;
        public static bool operator !=(BorrowedReference a, BorrowedReference b)
            => a.pointer != b.pointer;

        public override bool Equals(object obj) {
            if (obj is IntPtr ptr)

diff --git a/src/runtime/CustomMarshaler.cs b/src/runtime/CustomMarshaler.cs
@@ -189,49 +189,4 @@ public static ICustomMarshaler GetInstance(string cookie)
            return Instance;
        }
    }
-
-
-    /// <summary>
-    /// Custom Marshaler to deal with Managed String to Native
-    /// conversion on UTF-8. Use on functions that expect UTF-8 encoded
-    /// strings like `PyUnicode_FromStringAndSize`
-    /// </summary>
-    /// <remarks>
-    /// If instead we used `MarshalAs(UnmanagedType.LPWStr)` the output to
-    /// `foo` would be `f\x00o\x00o\x00`.
-    /// </remarks>
-    internal class Utf8Marshaler : MarshalerBase
-    {
-        private static readonly MarshalerBase Instance = new Utf8Marshaler();
-        private static readonly Encoding PyEncoding = Encoding.UTF8;
-
-        public override IntPtr MarshalManagedToNative(object managedObj)
-        {
-            var s = managedObj as string;
-
-            if (s == null)
-            {
-                return IntPtr.Zero;
-            }
-
-            byte[] bStr = PyEncoding.GetBytes(s + "\0");
-            IntPtr mem = Marshal.AllocHGlobal(bStr.Length);
-            try
-            {
-                Marshal.Copy(bStr, 0, mem, bStr.Length);
-            }
-            catch (Exception)
-            {
-                Marshal.FreeHGlobal(mem);
-                throw;
-            }
-
-            return mem;
-        }
-
-        public static ICustomMarshaler GetInstance(string cookie)
-        {
-            return Instance;
-        }
-    }
}
diff --git a/src/runtime/exceptions.cs b/src/runtime/exceptions.cs
@@ -95,24 +95,21 @@ internal static Exception ToException(IntPtr ob)
    /// </remarks>
    public static class Exceptions
    {
-        internal static IntPtr warnings_module;
-        internal static IntPtr exceptions_module;

        /// <summary>
        /// Initialization performed on startup of the Python runtime.
        /// </summary>
        internal static void Initialize()
        {
            string exceptionsModuleName = "builtins";
-            exceptions_module = Runtime.PyImport_ImportModule(exceptionsModuleName);
-
-            Exceptions.ErrorCheck(exceptions_module);
-            warnings_module = Runtime.PyImport_ImportModule("warnings");
-            Exceptions.ErrorCheck(warnings_module);
            Type type = typeof(Exceptions);
            foreach (FieldInfo fi in type.GetFields(BindingFlags.Public | BindingFlags.Static))
            {
-                IntPtr op = Runtime.PyObject_GetAttrString(exceptions_module, fi.Name);
                if (op != IntPtr.Zero)
                {
                    fi.SetValue(type, op);
@@ -147,8 +144,8 @@ internal static void Shutdown()
                Runtime.XDecref(op);
                fi.SetValue(null, IntPtr.Zero);
            }
-            Runtime.Py_CLEAR(ref exceptions_module);
-            Runtime.Py_CLEAR(ref warnings_module);
        }

        /// <summary>
@@ -348,9 +345,7 @@ public static void warn(string message, IntPtr exception, int stacklevel)
                Exceptions.RaiseTypeError("Invalid exception");
            }

-            Runtime.XIncref(warnings_module);
-            IntPtr warn = Runtime.PyObject_GetAttrString(warnings_module, "warn");
-            Runtime.XDecref(warnings_module);
            Exceptions.ErrorCheck(warn);

            IntPtr args = Runtime.PyTuple_New(3);

diff --git a/src/runtime/importhook.cs b/src/runtime/importhook.cs
@@ -155,7 +155,7 @@ public static unsafe NewReference GetCLRModule(BorrowedReference fromList = defa

            // find any items from the from list and get them from the root if they're not
            // already in the module dictionary
-            if (fromList != null && fromList != default)
            {
                if (Runtime.PyTuple_Check(fromList))
                {
@@ -224,7 +224,7 @@ public static IntPtr __import__(IntPtr self, IntPtr argsRaw, IntPtr kw)
            if (num_args >= 4)
            {
                fromList = Runtime.PyTuple_GetItem(args, 3);
-                if (fromList != default &&
                    Runtime.PyObject_IsTrue(fromList) == 1)
                {
                    fromlist = true;
@@ -297,7 +297,7 @@ public static IntPtr __import__(IntPtr self, IntPtr argsRaw, IntPtr kw)
            BorrowedReference modules = Runtime.PyImport_GetModuleDict();
            BorrowedReference module = Runtime.PyDict_GetItem(modules, py_mod_name);

-            if (module != default)
            {
                if (fromlist)
                {

diff --git a/src/runtime/pymodule.cs b/src/runtime/pymodule.cs
@@ -0,0 +1,41 @@
-Original file line number
+Diff line change
@@ Expand Up / @@ -9,7 +9,7 @@ @@
     using Python.Runtime;
-    namespace Python.EmbeddingPythonTest
     {
         public class TestNativeTypeOffset
         {
@@ Expand Down @@